KNIFE STEEL: Comprehensive Tables for Enlightenment
Posted: Fri Apr 09, 2021 9:29 pm
Hello All, some years back I became very interested in knife steel, specifically in how the different elements within the steel determined how they functioned, as well as how steel is made from the extraction of the ore, to forging, to heat treating, etc. I dived in to this field and read manufacturer data sheets which then lead to me reading literature on the various testing methods like Izod and Charpy impact testing, corrosion testing and the solutions used, I read scientific papers on the various elements in the steel especially Nickel and Nitrogen and how those elements react to each other, I read all about carbide formation and the different types of steel (such as Austenitic and Ferritic).
After all this research and cross referencing I decided to develop formulas that would accurately determine how a steel should perform in four important areas that impact knife users; Edge Retention, Ease of Sharpening, Corrosion Resistance, and Toughness (Ductility). I did this for two reasons, one being that when looking at knife steel ratings from various people and websites they were all very subjective and contradictory. This was in-part because they were not looking at the steel alone, but individual representative knives (which comes with some serious caveats which I will get into later). The other reason I did this was because I had already consumed a lot of info and wanted to put that knowledge to the test.
Before I post the tables I want to get into why comparing knives themselves is problematic as opposed to the steel by itself, and why I had to remove important elements from the formulas I used.
1. Quality Control: Unfortunately there are naturally going to be differences in the quality of knives produced, starting all the way back from roughly the beginning with ore extraction, followed by forging, followed by heat treating, followed by the knife design, etc. The same exact steel can be wildly different in performance depending on the degree of quality control through even just one phase of development. A good example of this is found with 440C, a steel that was "high end" when it was released but is now considered "budget" and unfortunately treated as such by manufacturers. I have observed a wide range of quality with 440C from older examples being really good to more modern stuff being actual junk, and everything in-between.
2. The Metallurgy Process: Not all processes are the same and thus not all steels are the same even if the chemical composition is the same. As an example the difference in performance between 154CM and CPM 154 is maybe not night-and-day but is considerable, and this is simply due to the fact that CPM 154 uses Particle Metallurgy (PM) for the molding process as opposed to a more traditional method for 154CM. The process Crucible uses creates a much more uniform (homogenous) carbide structure. In more conventional methods the carbide structure will be more irregular and less uniform and this has an impact on how the steel will perform. Add to this the amount of different processes that can be used (particle, powder, spray form, magnetic, etc.) and we can start seeing real differences in the steel despite the same composition of elements.
3. Heat Treat: Even if the quality of the steel formation was exceptional, heat treat can make or break a knife. If the heat treat was poorly done you can have irregularities in the hardness of the blade with portions being harder or softer than they should be. Even if the treat was uniform it can be undone if the blade is under-hardened or over-hardened. CPM S110V should be an excellent wear resistant (edge retention) but largely non-ductile (toughness) steel under quality treating, but if it was treated to a HR of 45 its edge retention would be laughable and it would be more ductile (great if that was the purpose of the steel, but it is not).
4. Blade Construction: Not only are quality and evenness important but so to is the grind and blade geometries. Angle of the edge can make a larger impact on edge retention, more then most would think.
For my formulas I could not factor the above things into them, as there is simply no way to account for all the variables and any values I came up with would be arbitrary. I didn't even mention the natural purity of some ores versus others
. Given all this the formulas only use the elements (Carbon, Chromium, Tungsten, Nitrogen, etc.) in the steel to create a score for grading. Certain things get underrepresented (like CPM S110V on Corrosion Resistance) due to not accounting for their carbide uniformity or other factors (Heat Treat namely), but I feel the formula works exceptionally well for ball parking observed performance regardless.
One last note, the lower the number for the Grade the better that steel is, the higher the number the worse it is.
After all this research and cross referencing I decided to develop formulas that would accurately determine how a steel should perform in four important areas that impact knife users; Edge Retention, Ease of Sharpening, Corrosion Resistance, and Toughness (Ductility). I did this for two reasons, one being that when looking at knife steel ratings from various people and websites they were all very subjective and contradictory. This was in-part because they were not looking at the steel alone, but individual representative knives (which comes with some serious caveats which I will get into later). The other reason I did this was because I had already consumed a lot of info and wanted to put that knowledge to the test.
Before I post the tables I want to get into why comparing knives themselves is problematic as opposed to the steel by itself, and why I had to remove important elements from the formulas I used.
1. Quality Control: Unfortunately there are naturally going to be differences in the quality of knives produced, starting all the way back from roughly the beginning with ore extraction, followed by forging, followed by heat treating, followed by the knife design, etc. The same exact steel can be wildly different in performance depending on the degree of quality control through even just one phase of development. A good example of this is found with 440C, a steel that was "high end" when it was released but is now considered "budget" and unfortunately treated as such by manufacturers. I have observed a wide range of quality with 440C from older examples being really good to more modern stuff being actual junk, and everything in-between.
2. The Metallurgy Process: Not all processes are the same and thus not all steels are the same even if the chemical composition is the same. As an example the difference in performance between 154CM and CPM 154 is maybe not night-and-day but is considerable, and this is simply due to the fact that CPM 154 uses Particle Metallurgy (PM) for the molding process as opposed to a more traditional method for 154CM. The process Crucible uses creates a much more uniform (homogenous) carbide structure. In more conventional methods the carbide structure will be more irregular and less uniform and this has an impact on how the steel will perform. Add to this the amount of different processes that can be used (particle, powder, spray form, magnetic, etc.) and we can start seeing real differences in the steel despite the same composition of elements.
3. Heat Treat: Even if the quality of the steel formation was exceptional, heat treat can make or break a knife. If the heat treat was poorly done you can have irregularities in the hardness of the blade with portions being harder or softer than they should be. Even if the treat was uniform it can be undone if the blade is under-hardened or over-hardened. CPM S110V should be an excellent wear resistant (edge retention) but largely non-ductile (toughness) steel under quality treating, but if it was treated to a HR of 45 its edge retention would be laughable and it would be more ductile (great if that was the purpose of the steel, but it is not).
4. Blade Construction: Not only are quality and evenness important but so to is the grind and blade geometries. Angle of the edge can make a larger impact on edge retention, more then most would think.
For my formulas I could not factor the above things into them, as there is simply no way to account for all the variables and any values I came up with would be arbitrary. I didn't even mention the natural purity of some ores versus others
. Given all this the formulas only use the elements (Carbon, Chromium, Tungsten, Nitrogen, etc.) in the steel to create a score for grading. Certain things get underrepresented (like CPM S110V on Corrosion Resistance) due to not accounting for their carbide uniformity or other factors (Heat Treat namely), but I feel the formula works exceptionally well for ball parking observed performance regardless.One last note, the lower the number for the Grade the better that steel is, the higher the number the worse it is.
Far too many obsess over and even brag about what steel is in their knife. 